In Thunar, xfdesktop, and xfce4-panel, no SVG icons get rendered. I'm currently Using Tango icons, which are all SVG (and 24x24 PNGs) and all I see are 24x24 icons (the max PNG size that comes with Tango). Reproducible: Always Steps to Reproduce: Upgrade to latest SVN and use a SVG icon theme.
I can't reproduce this. I'm using Rodent, and I removed all the PNG icons from the theme so there are only SVG icons. They work fine. Pease see the attachment to bug 1494 - try compiling that and running it with a few icon names you know should be present (just look in the scalable/ directory of the icon theme, and chop the extension off the filenames). Paste your program output here. Might also try removing the PNG icons as I did, at least to see what happens. GtkIconTheme might be preferring fixed-size icons for some reason. Not sure.
I downgraded my GTK and SVG icons came back. It would appear my issue is distro-specific.
If you upgraded across gtk minor versions (e.g. gtk 2.6.x to 2.8.x), you may need to recompile gdk's SVG loader, which isn't included with gtk itself. Or perhaps there's an updated package. I think gtk uses librsvg for SVG rendering, but that might have changed.
Moving invalid bugs to the /dev/null product.